[OT]:: Fully-automatic crossbow.

a***@stfc.ac.uk

2017-03-10 13:45:07 UTC

Haven't read/looked the links, but sounds like a variant of the repeating crossbow
https://en.wikipedia.org/wiki/Repeating_crossbow
Used by the Chinese and I believe the Romans as well. I recall a TV documentary where some archaeological historians in the UK built an example of Roman one, and were getting away several arrows/minute.

-----Original Message-----
Of RussellMc
Sent: 10 March 2017 13:19
Subject: [OT]:: Fully-automatic crossbow.
Thought about [TECH] ... :-)
Not as "cool" as Van Helsing's one.
And probably as much (or little) 'draw' as his.
BUT, it really works.
This one is electric powered (electric drill).
Van Helsing's was gas powered.
If you were throwing wooden 'stakes' at Vampires, this one may be as
effective, or not, as VH's.
Needs work. Lots. But, it works
http://youtu.be/tbKGjRoSofA
______________________________
*Van Helsing's version.*
I've seen people saying that VH's version is NOT a 'real' cross bow - that the
bow arms are cosmetic and do not participate in the action.
I'd have to watch the movie scenes to check but this "Replica" seems to do
things properly.
http://youtu.be/5BEZX6AprZI <- Excellent 44s video of replica "in
action".
People also suggested the Van Helsing draw energy was inadequate to be
useful. Given that we don't know what version of Hollywoodium is used in
the bow or the cylinder pressure, some wildguesstimates are in order. If the
pressure cylinder is 500cc and pressurised to 1000 psi (100 MPa) then stored
energy is about 100 kJ for Adiabatic expansion and about 350 kJ for
isothermal. Absent a blowtorch / heater assume ~= adiabatic and 100 kJ.
Lower pressure = lower energy (of course).
*Gas energy calculator
<http://www.tribology-abc.com/abc/thermodynamics.htm>*
A 9mm pistol manages around 500 J muzzle energy and a 357 magnum about 900J.
Even 200J would be exceptionally high for a crossbow bolt.
At 100% energy usage a 100 kJ reservoir gives about 500 shots.
Even at 20% overall that's 100 shots.
He may have to recharge between takes on occasion :-).
__________________________
*Bow images:*
https://cdn.globalauctionplatform.com/b2e3b1bd-9348-4b73-98fc-
a67400b6d7d3/918d9dd6-dfe5-43c7-ba54-ab7741917cc6/original.jpg
3D model ? https://www.behance.net/gallery/5109065/CrossBow-
Modelagem-3D
https://4.bp.blogspot.com/-
720Xwq0gsoo/V9Mm3SrbSJI/AAAAAAACZiM/LeLaLsYS634I_uHdjBbmQPpAA
HWg080jgCLcB/s800/Van%2BHelsing%2BCrossbow.jpg
*VH with bow*
Large. Good detail of mid section
https://s-media-cache-
ak0.pinimg.com/originals/1d/d4/ac/1dd4aca75ebfe4a8cb92553e07e26f92.jpg
https://forwhomthegearturns.files.wordpress.com/2013/12/crossbow.png
http://www.wallpaperup.com/uploads/wallpapers/2013/10/28/166475/big_t
humb_72e0eec40a9f4304bf2ce05da90dcb2e.jpg
http://4.bp.blogspot.com/-u3J5UW2tJTA/Th2Y_jtO-
wI/AAAAAAAAAWA/QM_2qV_T9NM/s1600/Jackman%2BVan%2BHelsing.jp
g
*MANY more images
<https://www.google.co.nz/search?q=van+helsing+crossbow&espv=2&tbm
=isch&source=lnt&tbs=isz:l&sa=X&ved=0ahUKEwjT7uHV-
cvSAhXKqlQKHdHDARsQpwUIEg&biw=1280&bih=713&dpr=1.5>*
& *more
<https://www.google.co.nz/search?q=van+helsing+crossbow&tbm=isch&tb
s=rimg:CVAFz4QP00x0Iji3eng7kSSCEkw0Thj5UBtTkssew55VM-
FJBSZHLKHjMWBv-
lpXqcbg6cU6mNzWL0QSbFOwWE17mCoSCbd6eDuRJIISESwZ5JXagDesKhIJTD
ROGPlQG1MR0ylTb9RKxr0qEgmSyx7DnlUz4RFjlDFTupPiYSoSCUkFJkcsoeMxE
WjlAgyPhkjtKhIJYG_16WlepxuARbHONUXLYsi4qEgnpxTqY3NYvRBEoNR6TnZ
mjbSoSCRJsU7BYTXuYEVsND_1c8gk-T&tbo=u&sa=X&ved=0ahUKEwib0NHw-
cvSAhXCHZQKHQXMCiQQ9C8IGw&biw=1280&bih=713&dpr=1.5>*
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